1. Field of the Invention
The present invention relates to a planar hermetic envelope and a planar image display apparatus. More particularly, the present invention relates to a planar image display apparatus in which an electron-emitting device and a light-emitting member are provided in a hermetic envelope whose interior is kept in a vacuous state or a reduced-pressure state.
2. Description of the Related Art
A hermetic envelope used in a field emission display (hereunder referred to as “FED”) or a surface-conduction electron-emitter display (hereunder referred to as “SED”) has a face plate (a front plate) and a rear plate, which are disposed so as to oppose each other. Peripheral edges of these plates are bonded (seal-bonded) to each other. Since the distance between the face plate the rear plate is kept on the order of mm, this distance cannot be filled with only a seal-bonding member. Therefore, in a seal-bond area between the peripheral edges of these plates, a rectangular frame-shaped side wall (rectangular frame) is disposed. Seal-bonding members are provided between a surface of the side wall (frame) and the face plate and between a surface of the side wall and the rear plate, respectively.
According to Japanese Patent Laid-Open No. 2003-203586, for setting the heights of seal-bonding members, spacers are provided between a frame and a rear plate and between the frame and a face plate, respectively. According to Japanese Patent Laid-Open No. 2005-174856, the width of a bonding part of a face plate and a frame is made different from the width of a bonding part of the frame and a rear plate.
Japanese Patent Laid-Open No. 2003-203586 does not discuss a structure in which a side wall, corresponding to the frame in the present application, abuts upon the face plate and the rear plate. In addition, this document does not discuss a structure in which the position where the side wall is bonded to the face plate is made different from the position where the side wall is bonded to the rear plate. Further, Japanese Patent Laid-Open No. 2005-174856 does not discuss a structure in which a spacer, which is a member corresponding to the frame according to the present application, abuts upon the first plate and the second plate.
FIG. 9 is a schematic sectional view of a vicinity of an edge of a related general hermetic envelope. A frame 3 is disposed between a face plate 1 and a rear plate 2. A first bonding part 4 is provided between the frame 3 and the face plate 1. A second bonding part 5 is provided between the frame 3 and the rear plate 2. The bonding parts 4 and 5 are formed by bonding the plates 1 and 2 to the frame 3 as a result of heating and melting seal-bonding members. Reference numeral 10 denotes a hermetic envelope interior, which is kept in a vacuous state or at a pressure below atmospheric pressure in a plasma display panel or an image display apparatus using an electron-emitting device.
In such a structure, a large residual stress is generated at portions (schematically shown by dotted ellipses in FIG. 9) of the plate 1 and the frame 3 near ends of the bonding part 4 of the face plate 1 and the frame 3. In addition, a large residual stress is generated at portions (schematically shown by alternate-long-and-short-dash-line ellipses in FIG. 9) of the rear plate 2 and the frame 3 near ends of the bonding part 5 of the rear plate 2 and the frame 3.
The residual stress resulting from forming the bonding part 4 by bonding the plate 1 and the frame 3 to each other with the bonding member and the residual stress resulting from forming the bonding part 5 by bonding the plate 2 and the frame 3 to each other with the bonding member overlap each other at the frame 3. Therefore, the resulting total residual stress is large.
The aforementioned residual stresses are noticeable when the bonding parts 4 and 5 are formed by bonding the plates 1 and 2 to the frame 3 as a result of heating and melting the bonding members.
When the hermetic envelope interior 10 is kept in a vacuous state or at a pressure below atmospheric pressure, bending stresses resulting from atmospheric pressure are, respectively, generated at a portion of the face plate 1 and a portion of the rear plate 2 that are, respectively, near an end of the interior-space-10 side of the face plate 1 and an end of the interior-space-10 side of the rear plate 2 (that is, the portions schematically shown by solid circles in FIG. 9).
As shown in FIG. 9, when the positions where the aforementioned residual stresses and the bending stresses are generated overlap each other, the face plate and/or the rear plate tend/tends to break. In addition, the frame 3 also tends to break. As a result, the reliability of the hermetic envelope is reduced.
This problem becomes more serious, for example, when the plates 1 and 2 are made thin or when the frame 3 is made thin (that is, the distance between the plates 1 and 2 is reduced). Such a problem also becomes more serious when the plates 1 and 2 and/or the frame 3 are formed of glass.
Therefore, from the viewpoint of making the hermetic envelope reliable in terms of breaking strength of the hermetic envelope, it is desirable that the stresses be lowered.